COMPUTING TOPIC COMPONENT ONE parts of a computer system Flashcards
What is the purpose of a computer?
to take data, process it, then output it
Why were computers built?
to help process data and complete tasks more efficiently than humans
What does a computer system consist of?
hardware and software that work together to process tasks
What is hardware?
the physical stuff that makes up your computer
What is software?
the programs or applications that a computer system runs
What are external pieces of hardware called?
peripherals
How are there many types of computers sytems?
- range from small (calculators) to big (supercomputers used by banks)
- general purpose (PCs) to dedicated systems (controlling traffic lights)
What are emedded systems?
computers built into other devices e.g. microwaves and TVs, they are usually dedicated systems
What do embedded systems do?
- often used as control machinery, they monitor and control the other parts to produce a desired result
- as they’re dedicated to a single task, they are usually easier to design, cheaper to produce and more efficient at their job than a general purpose computer
What does the power supply do?
provide power to motherboard, optical and hard drives, and other hardware
What does a case cooling fan do?
extracts hot air from inside the computer case
What does the CPU heat sink and cooling fan do?
keeps the CPU at a steady temperature
What does the CPU do?
processes all the data and instructions that make a computer work
What does the Hard Disk Drive do?
provide internal secondary storage
What does the motherboard do?
the main circuit board in the computer where all the hardware is connected
What does the optical drive do?
the reading/writing of optical disks
What does the processing power of the CPU depend on?
- clock speed
- number of cores
- cache size
What does the CPU architecture describe?
- the main components of the CPU
- how they interact with each other
- how they interact with other parts of the system
What are the three main parts of the CPU?
- the control unit
- the arithmetic logic unit
- the cache
What does the control unit do?
- in overall control of the CPU, main job is to execute program instructions following the fetch-decode-execute cycle
- controls the flow of data inside and outside the CPU
What does the arithmetic logic unit do?
- does all the calculations
- simple addition, subtraction, multiplication, division and compares the size of numbers
- performs logic operations such as AND, OR, NOT
- performs binary shifts
What does the cache do?
- very fast memory in CPU, slower than registers but faster than RAM
- stores regularly used data so that the CPU can access it quicker
- when the CPU requests data, it will first check the cache to see if it’s there, if not then it will check the RAM
- caches have a very low capacity and are expensive compared to the RAM
What are the different levels of cache memory?
- L1, L2, L3
- L1 is quickest but holds the least, L2 is slower but holds more, L3 is slowest but holds the most
What are the CPU registers?
- temporarily hold tiny bits of data needed by the CPU
- they are super quick to read/write to, much quicker than any form of memory
What does the Von Neumann architecture?
describes a system where the CPU runs programs stored in the memory
What do programs consist of in the Von Neumann architecture?
instructions and data which are stored in the memory addresses
What register does the control unit contain?
program counter
What register does the arithmetic logic unit contain?
accumulator
What other registers are in the CPU?
- memory address register
- memory data register
What is the function of the program counter?
holds the memory address of the instruction for each cycle
What is the function of the memory address register?
- holds any memory address about to be used by the CPU
- the address might point to data or an instruction
What is the function of the memory data register?
- holds the actual data or instruction
- may have been fetched from the memory or waiting to be written to the memory
What is the function of the accumulator?
stores intermediate results of calculations in the ALU
What does the memory hold in Von Neumann architecture?
holds the program instructions and the program data
What is one feature of the Von Neumann architecture?
only uses one memory for both data and instructions
What happens in the fetch instruction?
- copy memory address from the program counter to the MAR
- copy the instruction stored in the MAR address to the MDR
- increment the program counter to point to the address of the next instruction ready for the next cycle
What happens in the decode instruction?
- instruction in the MDR is decoded by the control unit
- control unit may then prepare for next step e.g. loading values into MAR or MDR
What happens in the execute instruction?
- the instruction is performed
- this could be: load data from memory, write data to memory, do a calculation or logic operation using ALU, change the address in the program counter, or halt the program
What is the difference between the program counter and the MAR?
- program counter starts off each cycle by pointing to the instruction
- MAR has to process all memory address for both data and instructions which means its value might change several times each cycle
What does the memory contain?
all the instructions that the CPU follows
What is the RAM used as?
the main memory in the computer
What is the main memory?
where all data, files and programs are stored while they’re being used
How is RAM used?
- when the computer boots up, the OS is copied from secondary storage to the RAM
- when applications, documents or files are opened, they are copied from secondary storage to RAM and stay in the RAM until they are closed
What is the speed of RAM like?
slower than the CPU cache but faster than secondary storage
How is virtual memory created?
- computers have a limited amount of RAM, as applications are opened, the RAM fills with data
- when RAM is full, computer needs somewhere else to put application data
- it moves data that hasn’t been used recently to a location on secondary storage known as virtual memory
When is virtual memory needed?
if there are too many applications open, or there is a memory-intensive application, or both
How are transfer rates slower when using virtual memory?
- if the CPU needs to read data from virtual memory, it must transfer the data back to RAM
- this is slow as data transfer rates are slower on secondary storage than on RAM
How does using virtual memory make a computer slow to respond?
- when switching between applications, while data for one application is swapped for another in virtual memory
- when using a memory-intensive program, due to data constantly moving between virtual memory and RAM just to keep the program running
What is the BIOS?
a type of firmware, hardware-specific software built into a device
How is ROM found in a computer?
a small factory-made chip built into the motherboards
What does ROM on a computer contain?
- all the instructions the computer needs to properly boot up
- these instructions are known as the BIOS
What does the CPU do with ROM when booted up?
- reads instructions from ROM
- tells CPU to perform self-checks and set up the computer
- e.g. test the memory is working OK, see what hardware is present and copy the operating system onto the RAM
How can the BIOS be updated
you can flash the BIOS on a ROM chip
What type of memory do ROM chips use?
flash memory
What is flash memory?
- very common type of non-volatile memory that stores data in electrical circuits by trapping electrons
- used in SD cards, USB sticks, SSD
How does clock speed affect CPU performance?
- higher the clock speed, the higher the number of instructions per second
- is possible to overlock, but can make CPUs overheat which can cause crashes or damage to the system, high performance cooling solutions are usually needed
How does the number of cores affect CPU performance?
- each core in a CPU processes data independently
- more number of cores, the more instructions it can carry out at once so the faster it can process a bunch of data
- most PCs and smartphones have 4 or more cores
Why doesn’t doubling the number of cores double the performance of a CPU?
- software needs to be designed to be able to use multi-core processing
- not all processing tasks split evenly between the cores, some steps will depend on others meaning some cores may be waiting for another core to catch up
How does cache size affect CPU performance?
a large cache means that the CPU faster access to more data it needs to process
How does RAM affect computer performance?
- too little RAM means that the computer may have to rely on virtual memory
- more the RAM, the more applications or more memory-intensive programs the computer can run making the system smoother
What are GPUs?
- specialised circuits for handling graphics and image processing
- relieve the processing load on CPUSs, freeing it do other things
How do GPUs work?
- computers have a basic GPU integrated into the motherboard or CPU, for better graphics performance a dedicated GPU is often used
- using high-end graphics cards can greatly improve performance in graphics-intensive applications
What is tertiary storage?
- used for long-term data storage
- mainly used for archives and back-ups of massive amounts of data
What is secondary storage hold?
all data when not in use
How does a HDD work?
- made up of a stack of magnetised metal disks spinning at a rate between 5400 and 15000 rpm
- data is stored magnetically on small areas called sectors on circular tracks
- read/write heads on a moving arm are used to access sectors on the disks
Why are HDDs reliable?
- portable HDDs are popular for backing up and transporting large amounts of data
- despite moving parts, HDDs are long-lasting and reliable, although data could be affected after a sudden impact such as a drop
How do SSDs work?
-internal storage with no moving parts, most of them use flash memory
What is an advantage for SSDs when using a computer?
- using SSDs can give quicker times for booting up the system and opening programs and files compared to a HDD
- like HDDS, portable SSDs can be used to back up and transport large amounts of data
What are some other types of flash storage?
- pen drives and memory cards
- much slower than SSDs and have a much shorter read/write life
- used to expand the storage capacity of small devices such as cameras or smartphones
- they have a very large storage capacity in relation to their tiny size
What are some advantages of HDDs?
- cheaper
- higher capacity
- have a longer read/write life than SSDs, SSDs can only be written a certain number of times before they start to deteriorate
What are some advantages of SSDs?
- faster
- don’t need defragmenting
- more shock-proof
- HDDs make some noise, SSDs are silent
How much data can optical discs store?
- CDs can store around 700MB
- DVDs can hold around 4.7GB
- Blu-Rays can hold around 25GB
What are the three forms that optical disks can come in?
- read only: CD-ROM, DVD-ROM, BR-ROM
- write-once: CD-R, DVD-R, BR-R
- rewritable: CD-RW, DVD-RW, BR-RW
How does an optical disc work?
- data is stored as microscopic indentations on the surface of the disc
- data is read by shining a laser beam on the surface and detecting changes in position of reflected beam
Why are optical discs declining in usage?
- as Internet speeds, new streaming and downloading servies have eliminated the need for optical discs
- modern devices such as phones, tablets, and new computers don’t have optical drives
- DVD-Rs and DVD-RWs used to be popular for backing up data but can’t compete with flash storage due to low capacity per disc, very slow read/write speeds, and poor reliability of RW discs
What are some advantages of optical discs?
- very cheap
- portable
- won’t be damaged by water or shocks (although easily scratched)
What are advantages of magnetic tape?
- greater storage capacity than HDDs
- extremely low cost per GB
What are magnetic tapes used for?
- large organisations in archive libraries who store large amounts of data
- businesses who need to do large frequent back-ups
How do magnetic tapes work?
- come in plastic cassettes containing reels of tape
- cassettes require a special tape drive for reading/writing
How is magnetic tape read/written to and from?
- read/writing takes place from beginning of tape until end unless computer stops it
- this means it has a slow read/write speed when finding specific data but a fast read/write speed when it’s in the correct place
Rank of average read/write speed from slowest to fastest?
- optical disc
- memory card
- magnetic tape
- HDD
- SDD
Rank of average cost per GB from cheapest to priciest?
- magnetic tape
- optical disc
- HDD
- memory card
- SSD
Rank of average capacity from lowest to highest?
- optical disc
- memory card
- SSD
- HDD
- magnetic tape
What is system software?
- software designed to maintain and run a computer system
- the most important one is the OS
What are the main functions of the OS? (6)
- communicate with internal and external hardware via the device drivers
- allowing the user to interact with the computer via a user interface
- provide a platform for the different applications to run on
- allow the computer to multi-task by controlling memory resources and CPU
- deal with file management and disk management
- manage the security of the system e.g. through user accounts
How does the OS use device drivers?
- to allow communication with the internal hardware and peripherals connected
- every piece of hardware connected to the computer system requires a device driver which acts as a ‘translator’ for the signals between the OS and the hardware
What will happen with device drivers when the computer is booted up?
- when the computer is booted up, the OS will choose the correct device drivers for the hardware that it detects
- if new hardware is detected, the system will install new device drivers for that hardware
How are device drivers updated?
- device manufacturers may release updates to the device drive in order to fix bugs, improve hardware or add features
- updates may be installed automatically by the OS or manually by the user
What are GUIs?
- most common type of user interface
- designed to be easy for everyday users by making them visual, interactive and intuitive
How are GUI systems optimised?
- optimised for specific input methods
- in the past, GUIs have been WIMP-based (windows,icon,menus,pointers)
- Android and iOS created for touchscreen devices using finger gestures such as pinching and swiping in place of a mouse
What is a command-line interface?
- text-based interface
- user enters specific commands to complete tasks
- command-line interfaces are less resource-heavy than GUIs
How are command-line interfaces suitable?
- aren’t suitable for everyday users
- for advanced users, they can be far more efficient and powerful than GUIs
- can be used to automate programs using scripts
How do OSs provide a platform to run applications?
by configuring hardware so they can use it and giving access to the CPU and memory
What are OSs that can run multiple applications at the same time called?
multi-tasking OSs
How does the OS help the CPU carry out multi-tasking efficiently?
- when an application is opened, the OS moves the application to the memory in addition to other parts if they are needed
- the OS determines if an application has been used recently, if not then it may be removed from memory
- to run multiple applications, the OS needs to make sure applications don’t override or interfere with each other
- only one application is processed by the CPU at a time, so the other processes must wait
- the OS divides CPU time between open applications and may prioritise certain processes so instructions can be executed in most efficient order
- when required, OS organises data movement to and from virtual memory
How does the OS ensure that applications don’t interfere or override with each other?
a memory manager allocates certain applications certain memory addresses, to make sure their processes are placed in certain locations
How do files work on a computer?
- computers store data as files
- images, music, videos and spreadsheets are all just collections of data
- file extensions tell the computer which software should be used to open the file
How is the OS responsible for file management?
- manages data into a hierarchical structure
- deals with movement, editing and deletion of data
How does the OS manage files on the hard disk?
- splits the physical disk into storage sectors, decides which sectors to write data to and keeps track of free space on the disk
- ideally, the data for a single file would be stored in adjacent sectors but this isn’t always possible
How can OS use utility software to manage files?
- file compression can reduce the size of individual files
- encryption can secure the content of files
- defragmentation can help organise and manage the hard disk by moving all the free space together
What is a single-user OS?
- allow only one user to access the computer at once
- most modern OSs (macOS, Windows 10) are like this even if they allow multiple user accounts or are connected to a network
What is a multi-user OS?
- allow several users to access the computer at the same time
- often used on mainframes (huge supercomputers) and allow multiple users simultaneous access
- e.g. ATMs allow thousands of people to access a bank’s mainframe at the same time
How are OSs responsible for user account control?
- user accounts allow users to access specific data or resources on a computer system
- on most desktop OSs, each user has access to their own personal desktop and files but no one else’s
How do OSs use anti-theft measures for user accounts?
- may have anti-theft measures to prevent other users accessing locked devices or accounts to steal information
- user accounts may be password or pin-protected
- some deices also require user to draw a specific pattern, or have fingerprint or retina scanners
What is utility system software?
- helps to maintain or configure a computer
- much useful utility software already installed on OS but more may be installed by user to perform additional tasks
How does fragmentation occur on a HDD?
- as files are moved, deleted or change size, lots of small gaps begin to appear on the disk
- when writing files to disk, OS splits files into smaller chunks to fill gaps on disk
- over time, the disk becomes more fragmented
- this makes reading/writing files slower as the read/write head has to move back and forth across the disk
What does defragmentation software do?
- reorganises data so that fragmented files are back together
- also organises files so that all free space is collected together which prevents further fragmentation
Why don’t SSDs need defragmentation?
- as SSDs have flash storage with no moving parts, fragmentation isn’t a problem as they can access data just as quickly no matter how it’s stored
- because SSDs have a limited amount of read/writes, defragmentation can shorten their lifespan
What is a backup?
- a copy of a computer system’s files and settings stored externally
- this means data can be recovered in the event of data loss
What is a backup utility?
software with facilities such as scheduling of regular back ups, creating rescue disks, disk images and options for full or incremental backups
What is a full backup?
- where a backup is made of every file from the system
- often take a large storage space
- take longer to backup
- however, are quicker to restore from
What is an incremental backup?
- where only files that have been created or edited since the last back up are copied
- use less storage space
- take much quicker to backup
- take much longer to restore, need to restore last full backup plus every incremental back up since then
What is compression software?
- reduces size of files so they take up less disk space
- used frequently on the Internet so that they take less time to download
- common file extensions include .zip and .rar
- files need to be extracted before they can be used
What is encryption software?
- encrypts data so that third-parties can’t access it
- encrypted data can be decrypted using a special key
What is open source software?
- software where the source code is made freely available
- users may legally modify the source code to create their own spin-off software which can be shared under the same license and terms of the original software
What are some examples of open source software?
- Mozilla Firefox
- GIMP
- VLC media player
What is Linux?
- hugely successful open source OS released in 1991
- hundreds of Linux-based OSs have been developed and shared over the years such as Ubuntu and Android
What does popular open source software have?
- supported by a strong online community
- users actively help to improve software, anyone can play with source code and suggest bug fixes and improvements to original developers
What are some advantages of open source software?
- usually free
- made for the greater good, not profit
- software can be adapted by users to fit their needs
- wide pool of collaborators can be more creative and inventive than programmers of one company
- usually secure and reliable, any problems are quickly fixed by community
What are some disadvantages of open source software?
- small projects may not get regular updates, so could be buggy or have unpatched security holes
- may be limited user documentation
- no warranties if something goes wrong
- no customer support
- companies making custom software based off open source software may not want competitors to see software code but are left with no choice
What is proprietary software?
- usually paid for
- only the compiled code is released and the source code is kept secret
- proprietary software licenses may restrict the modifying, copying and redistribution of the software
- businesses tend to use as it has better customer support options
What are some advantages of proprietary software?
- comes with warranties, documentation and customer support
- should be well-tested and reliable as the company’s reputation relies on this
- fixes and updates come regularly
- usually cheaper for companies than developing their own custom built software
What are some disadvantages of proprietary software?
- can be expensive
- software may not exactly fit a user’s needs and there’s nothing they can do about it
- software companies may not maintain older copies after warranties expire, they’ll want people to buy latest product
